Making The Diagnosis

The platelet count of reactive thrombocytosis accompanying inflammation, bleeding, cancer, or infection is rarely elevated to the degree seen in ET. A Serum, fer-retin level is helpful in excluding iron deficiency (bleeding as a cause of thrombocytosis). Thrombosis never occurs in secondary thrombocytosis. All patients considered to have ET should have cytogenetic or molecular studies performed to exclude CML, a disease that can present in a patient with an increased platelet count and only a modest elevation of the WBC. For patients with borderline or moderately elevated RBC values, a Cr51 RBC mass study is mandatory to exclude PV. JAK2